1. Field of the Invention
The invention relates to radio telecommunications systems, and more particularly, to a method and system for enabling a plurality of mobile telephone users to share a common subscription which includes certain limitations on the services available to the members of the mobile telephone user group sharing that subscription.
2. Description of the Related Art
In recent years the growth of mobile radio telephone systems, particularly cellular radio telephone systems, has been phenomenal. Such systems enable complete telecommunications facilities to be furnished to a community, a city, or even an entire country without the time and expense of installing a wire line infrastructure. Moreover, mobile radio telephone systems enable the availability of communications resources to a subscriber regardless of the physical position of the subscriber within the system or whether the subscriber is moving or stationary.
Each mobile radio telecommunication system operator must make a very large investment in infrastructure equipment, including mobile switching centers and base stations, in order to serve the geographic territory for which it has a license. Thus, in order to maximize its revenue and return on this investment, an operator desires to utilize as much of the available radio frequency spectrum within its area as possible by maximizing the subscribers who use the system. It is in the best interest of both mobile radio telephone system operators and their subscribers to increase the number of mobile telephones in use within the system. However, since there is a separate charge for each subscription enabling access to the system, certain classes of subscribers, such as family units and small companies, hesitate to incur the expense of a separate mobile phone subscription for each person in that unit. From the system operators' view point, an increase in the number of subscriber stations having potentially simultaneous access to the system increases the demand for radio traffic channels within the system and contributes to a major problem in expanding the capacity of mobile radio telephone systems and networks. For this reason, it would be a major advantage to allow a single subscription to be shared by several individuals within a user group thus enabling a lower communication cost per user than a single subscription for each of the users in that group.
Certain cellular radio system operators have attempted to solve this problem. One such system, for example, offers a subscriber service which includes a single subscriber number but two subscriber information module (SIM) cards each usable separately in different mobile telephone stations. Each card may be inserted into a separate mobile telephone terminal and used independently of one another for outgoing calls. An incoming call directed to the common subscriber number is completed to the terminal which was used last and an incoming call which is not answered by the terminal to which it is directed is automatically rerouted to the other terminal. This service is particularly adapted to separate a business usage of the subscription from a private usage thereof in that each of the two terminals is charged independently of the other. While it would be possible for two persons to share a single subscription under this service, it would have certain limitations and disadvantages.
Similarly, certain international telecommunications standardization bodies, for example, the International Telecommunications Union, have specified integrated services digital network (ISDN) services which include multiple subscriber numbers that provide the possibility of assigning multiple ISDN numbers to a single interface in a fixed ISDN network. For example, U.S. Pat. No. 5,392,346 describes a system which includes this feature. However, this system is limited to fixed wireline ISDN networks because of its unique features and architecture.
In addition, U.S. patent application Ser. No. 08/585,149, filed Jan. 10, 1996 in the name of Carlsson et al., entitled "Cellular Telecommunications Systems Having Selectively Associatable Usage Parameters" and assigned to the assignee of the present application describes a system for registering several users on a single subscription. In the system of the Carlsson et al. application all of the registered users are allowed to seize a traffic channel simultaneously which, from the system operator's point of view is somewhat of a disadvantage in that it increases the traffic on the network without the revenue of multiple subscriptions. The system operator would much rather encourage separate subscriptions for which a subscription fee is received for each potential access. Another disadvantage of the Carlsson et al. system is that all of the users on a common subscription are governed by the same conditions associated with that subscription. In the case of a family unit having a single subscription it would be more desirable to have individual conditions associated with each individual member of the family having possible access to the network.
A disadvantage of the prior art systems is that in order to secure a broad usage of mobile telephones among certain groups of users such as families and small businesses, such usage is inhibited by the necessity of each user having to sign an individual subscription agreement with an operator and incur substantial initial and periodic costs in association with that subscription. In addition, from the system operator's point of view, the number of available traffic channels is a critical resource of the system and the operator has a substantial interest in spreading system traffic across time in order to maximize the utilization of these resources.
The present system addresses these problems and solves them with other advantages which will be clear from the following description of the invention.